Engine cooling system



V- 1944- w. GILUNDQQUIST I 2,362,015

ENGINE COOLING SYSTEM Filed March 22, 1945 20 22 ENG/NE RADIATOR FAILENG/NE PUMP RA D/ATORI ENG/NE /2 INVENTOR W7LT0- G. L u/vo u/s'r.

BY RADIATOR ATTORNEY Passed Nov. 1, 1944 Wilton G. Lundqulst, Hohokus,

Wright Aeronautical Corporation,

of New York Application March 22, 1943, Serial N. 1., assignor to acorporation 13 Claims. (c ams-174) and is particularly directed to asealed liquid cooling system employingforced circulation.

This invention relates to a liquid cooling systems Liquid coolingsystems for aircraft engines con- I sist essentially of a liquid-cooledjacket for the engine, a pump for circulating liquid therethrough, aradiator, an expansion tank, a liquid connection from the jacket to theexpansion tank. and a pressure relief valve 'It is an object of thisinvention to provide a novel and simple means for increasing thepressure on the liquid in the expansion tank to a suilicient extent toprevent boiling of the liquid in the -ciflcaily. the invention consistsinthe provision of -means'for-raising the temperature of the liquid inthe expansion tank thereby increasing the vapor pressure in this tank.

Other objects of the invention will become apfor the expansion tank.

or-at any other point in the system. 'Speparent irom reading the annexeddetailed description in connection with. the drawing, in which: i

Figs. 1, 2 and 3 schematically illustrate three different embodiments ofthe invention; and Fig. 4 is a detail view of a safety valve. Referringto the preferred embodiment illustion engine is indicated at Ill and aliquid circulating pump it is driven from this engine by a shaft ll. Aconduit 16 connects a cooling radiator is with the inlet of the pump l2.and a conduit 20 connects the delivery side of the pump to theenginecoolant Jacket. A conduit 22 provides a return from the enginejacket to the radiator thereby completing the main liquid circulatingcircuit including the engine jacket radiator and pump.

An expansion tank 24 is connected to the main circulating circuit at theinlet side of the pump bya conduit 28; A line 28 connects an upperportion of the jacket at its discharge end with the In actual practicethe cross-sectional closed'position by a spring 42. to allow valveelement 40 to open when the pressure inside the expansion tank becomesexcessive. In addition a valve element ll cooperates with a a centralopening in the valve element". The

valve element 44 is biased closed by a spring 48 of such strength thatthis valve opens when the drops below, The liquid cooling systempressure inside the expansion tank atmospheric pressure. so fardescribed is conventional.

. During the operation of the system it is desirable that all air beeliminated from the system. Accordingly, a conventional thermostaticradiatortype air-vent valve Si is connected to the space 32 above theliquid in the expansion tank 24. Instead of the air-vent valve 3 I asmall opening may be provided at an upper portion of the expansion tankto permit the escape of the space 32 rises. In normal operation, thetemperature of the liquid in the expansion tank rises above 212? F. sothat with water in the expansion tank, the vapor pressure in space 32will exceed atmospheric pressure and force the air out of this space.Accordingly, the pressure in the space 32 above the liquid in theexpansion tank is the vapor pressure of the liquid corresponding to theparticular temperature of the liquid in the tank.

i. e.,' during normal operation the liquid in the trated in Fig. 1, aliquid-cooled internal combusexpansion tank is right at the boilingpoint for the temperature and pressure conditions existing in the tank.For example, if some of the vapor in the space 32 were suddenlycondensed, the resulting reduction in pressure in this space would causeboiling of the liquid since for this new pressure the temperature of theliquid in the tank would be above its boiling point.

The pressure at the inlet of pump I2 is equal to the vapor pressure inthe space 32 plus the pressure head due to the elevation of the tank 2relative to the pump. In a liquid cooling system for an aircraft engine,the elevation of the tank 24 relative to the pump is necessarily quitesmall so that the pressure at the inlet of the pump it can only beslightly greater than the vapor pressure in the space 32. Also, becauseof the cooling eflect produced by the radiator it, the inlet pumptemperature is less than the temperature in the tank 24. Thus,.thetemperature and pressure conditions of the liquidat the pump inlet aresuch that at this point in the system the liquid is somewhat below itsboiling point. However, as the liquid is picked up by the pump it ismomentarily accelerated whereupon there is-a' substantial conversion ofliquid pressure head to velocity head. As a result, the temperature ofthe liquid in the pump may be above the boiling point of the 7 liquidfor this reduced pressure whereupon the boiling of the liquid occurs inthe pump.

air as the pressure in g creased suiiiciently This boiling in the pumpconsiderably reduces the efliciency of the pumpand it is an object oithis invention to eliminate this boiling so that the inlet temperatureoi approximately 235 F., this increase in vapor pressure in space 32would normally be sufllcient to prevent boiling in the pump.

In order to raise the temperature of the liquid in the expansion tank,the engine exhaust discharging through the manifold 38 is passed throughan engine-exhaust heater 34 in heat exchange relation with the liquidreturning to the expansion tank through the line 28. The pressure riseproduced by thepump l2 provides ior circulation oi liquid through thevent line V2!! to the expansion tank so that the heater 84 serves toheat up the liquid in the expansion tank 24. A thermostatic valve 28 islocated in the line 28 to control the flow therethrough into theexpansion tank 24 and a thermally responsive bulb l8,

. located in the expansion tank 24, is connected to and regulates thisvalve 38 so as to maintain a desired temperature in the expansion tank24. In this way the vapor pressure in space 32 is into prevent boilingin the pump l2. A conventional by-pass or other means may be provided.to prevent valve Slit-om completely closinsthelinefl; i

At this point it may be noted thatii a-suiiiclent temperature rise ismaintained'through the engine jacket, the temperature inthe expansiontank 24 and the depending vapor pressure in the space 82 may be highenough to prevent boiling in the pump I 2 without the addition oi theheater 34.

In the modification illustrated in Fig. arate iiow path 48 is providedfor returning liquid to the expansion tank direct from the outlet of thepump I2. The exhaust heater 34' is placed in heat exchange relation withthe line 40 and a thermostatic valve 30' by a thermally responsive bulb38' located in the expansion tank. The heater 34' is thereby operativeto raise the temperature in the expansion tank to the desired extent.The balance of the cooling system illustrated in Fig. 2 is similar to.55

Fig. 1. The construction oi'- Fig. 1 has the advantagein that since theliquid being returned through line 28 has been in heat exchange relationwith the engine, it is not necessary for the heater 34 to impartreturning to this line as compared to the amount of heat required to beabsorbed by the liquid returning through line 48 in Fig. 2.

The modification. illustrated in Fig. 3 is similar to Fig. 1 except thatinstead of placing the engine exhaust heater in the conventional ventline 2|, a separate line II is provided in parallel with the line 2!"and an engine exhaust, heater 24" is placed in II. The thermostatic flowcontrol valve 3." is placed in this line under the control of athermally responsive bulb ll" located in the expansion tank. Fig. 3 isotherwise similar to Fig. i.

In all three modifications, an engine exhaust heater is used to heatliquid returning to the expansion tank. However, the invention is not solimited since obviously other means may be em-- ployed for heating theliquid in the expansion tank. The amount of heat it is necessary tointroduce into the cooling System by the heating of the liquid in theexpansion tank is quite small due to the small magnitude to the flow inthe expansion tank circuit and probably does not amount to more than 2%oi the heat rejection of the engine.

In each of the above described pressurized cooling systems, the systemis operated at a pressure sumciently high to prevent boiling at anypoint in the system. Other means have been suggested for obtaining thisresult, for example, it has been proposed to supercharge the space 32with an air pressure sufficient to raise the liquid pressure in the pumpto prevent boiling therein. It has also been proposed to trap air in theexpansion tank to obtain the required additional pressure. However,applicant's system has the advantage of completely eliminating air-sincethe entire system is, fil led with coolant liquid and coolant vapor.

' This improves the performance 01' the pump since in this line iscontrolled pansion tank for said I combustion it is only required tohandle liquid and also reduces the corrosion characteristics of theliquid coolant since it is not combined with any entrained air. Anadditional advantage of the system illustrated in Fig. 1 is that theheater 84 would tend to prevent freezing of the liquid in While I havedescribed my invention in detail in its present preferred embodiment, itwill be obvious to those skilled in the art, aiter understanding myinvention, that various changes and modifications may parting from thespirit or scope thereof. I aim in the appended claims to cover all suchmodiflcations and changes.

I claim as my invention:

- 1. In a sealed liquid cooling system for an internal combustionengine, a pump for circulating liquid through a. jacket for said engine,an expansion tank for said liquid connected to the inlet side oi saidpump, and a heater utilizing the engine exhaust gases for heating theliquid in said expansion tank.

2. In a liquid cooling system for a mechanism, a pump for circuating acooling liquid in heat exchange relation with said mechanism, anexliquid connected to the inlet side oi the pump, and means operative tomaintain the vapor pressure of the liquid in said tank above a,predetermined value. I

3., In a liquid cooling system tor an internal engine, a pump forcirculating liquid through a cooling Jacket for said engine, a ventedexpansion tank for said liquid connected to the the vent line 28.

\ inlet side of the pump, and anengine-exhaust as much heat to theliquid heater for heating the liquid in said expansion tank. 1

4. In a liquid cooling system for an internal combustion engine, a pumpfor circulating liquid thromh a. cooling jacket for said engine, onexpansion tank for said liquid connected to'the inlet side of said pump.a conduit extending from an upper portion and adjacent the discharge endheat exchange relation with the line I 76 pension for oi said Jacket tosaid expansion tank, and a heater utilizing the engineexhaust gases forheating the liquid r to the expansion tank through saidconduit.

5. In alliquid cooling system for an internal combustion engine, a pumpfor circulating liquid through a cooling jacket for said engine, anexsaid liquid connected to the be made therein without deinlet side ofsaid pump, a conduit extending from an upper portion and adjacent thedischarge end of said jacket to said expansion tank, a heater utilizingthe engine exhaust gases for heating the liquid returning to theexpansion tank through said conduit, and a thermostatic valve in saidconduit responsive to .the temperature of the liquid in the expansiontank.

6. In a liquid cooling system for an internal combustion engine, a pumpfor circulating liquid through a cooling jacket for said engine, anexpansion tank for, said liquid connected to the inlet side of saidpump, conduit means through which said pump is operative to return apart of said circulating liquid to said expansion tank, and meansoperative to maintain the vapor pressure of the liquid in said tankabove a predetermined value.

'1. In a liquid cooling system for an internal combustion engine, a pumpfor circulating liquid through a cooling jacket-for said engine, anexpansion tank for said liquid connected to the inlet side of said pump,conduit means through which said pump is operative to return a part ofsaid circulating liquid to said expansion tank, an engine-exhaust heaterfor heating the liquid returning through said conduit means, and athermostatic valve controlling the flow through said conduit means inresponse to the temperature in said expansion tank.

8. In a liquid cooling system for an internal combustion engine, a pumpfor circulating liquid through a cooling jacket for said-engine, aradiator disposed between the discharge end of said jacket and the pumpinlet for cooling said liquid, an expansion tank for said liquidconnected to the inlet side of said pump, and means operative tomaintain the vapor pressure of the liquid in said tank above apredetermined valve.

9. In a liquid cooling system for a mechanism, a pump for circulating acooling liquid in heat exchange relation with said mechanism, anexpansion chamber for said liquid connected to the inlet side of saidpump, and means including a flow passageway through which said liquidflows into said chamber from a point downstream of said pump formaintaining a desired liquid vapor pressure in said chamber.

10. In a liquid cooling system for a mechanism, a pump for circulating acooling liquid in heat exchang relation with said mechanism, a radiatordisposed between the discharge end of said jacket and the pump inlet forcooling said liquid, an expansion chamber for said liquid connected tothe inlet side of said pump, a passageway through which said pump isoperative to return liquid to said chamber, and means controlling theflow through said passageway and operative to maintain a desired liquidvapor pressure. in said chamber.

11. In a liquid cooling system for a mechanism, a, pump for circulatinga cooling liquid in heat exchange relation with said mechanism, anexpansion tank for said liquid connected to the inlet side of said pump,and means for maintaining the vapor pressure of the liquid in said tankabove a predetermined value, said means including a liquid passagethrough which warm liquid enters said expansion tank.

12. In a liquid cooling system for a mechanism, a, pump for circulatinga cooling liquid in heat exchange relation'with said mechanism, anexpansion tank for said liquid connected to the inlet side of said pump,andmeans for maintaining, the vapor pressure of the liquid in said tankabove a predetermined value, said means including a liquid passagethrough which liquid heated by said heat exchange circulation relativeto said mechanism is returned to said expansion tank.

13. In a liquid cooling system fora mechanism, a pump for circulating acooling liquid in heat exchange relation with said mechanism and througha cooling radiator for said liquid, an expansion tank for said liquidconnected to the inlet side of said pump, and means for maintaining thevapor pressure of the liquid in said tank above a, predetermined value,said means including a liquid passage through which warm liquid isreturned by said pump to said expansion tank.

WILTON G. LUNDQUIST.

